US subprime mortgages written during the first half of the year are going delinquent at the fastest rate this decade, according to a report from Moody’s on Thursday that analyses home loans used to back bonds. The average rate of “serious loan delinquencies” in the 2007 bonds is higher than those created last year, a vintage considered to be one of the worst-performing ever.

The ratings agency defines “serious delinquency” as loans that are 60 days or more overdue, and includes properties in foreclosure and those already foreclosed upon. Typically, subprime mortgages are used to back bonds sold to institutional investors.